In the human brain, a dedicated unit is entrusted with keeping in the back of one's mind the road not taken

Imagining the future self through thought experiments. Kentaro Miyamoto, Matthew F.S. Rushworth, Nicholas Shea. Trends in Cognitive Sciences, February 17 2023. https://doi.org/10.1016/j.tics.2023.01.005

Highlights

. Performing thought experiments – thinking about what consequences might follow from a course of action that has not yet been pursued – is an important element of mental life in both human and non-human primates.

. Recent studies have found that both frontopolar cortex (FPC) and anterior lateral prefrontal cortex (alPFC) contribute to introspective evaluation of beliefs about events even when they are not directly observed.

. FPC and alPFC are essential for tracking and evaluating counterfactual choices (what one might have done) and possible future choices (what one might do), respectively.

. We propose a theoretical model in which the interplay between FPC and alPFC enables thought experiments.

Abstract: The ability of the mind to conceptualize what is not present is essential. It allows us to reason counterfactually about what might have happened had events unfolded differently or had another course of action been taken. It allows us to think about what might happen – to perform 'Gedankenexperimente' (thought experiments) – before we act. However, the cognitive and neural mechanisms mediating this ability are poorly understood. We suggest that the frontopolar cortex (FPC) keeps track of and evaluates alternative choices (what we might have done), whereas the anterior lateral prefrontal cortex (alPFC) compares simulations of possible future scenarios (what we might do) and evaluates their reward values. Together, these brain regions support the construction of suppositional scenarios.

Keywords: prospective metacognitioncounterfactual simulationsthought experimentsprimates

Big is bad, more rapacious, more unethical: Stereotypes About Organizational Size, Profit-Seeking, and Corporate Ethicality

Big Is Bad: Stereotypes About Organizational Size, Profit-Seeking, and Corporate Ethicality. Andrea Freund, Francis Flynn, Kieran O’Connor. Personality and Social Psychology Bulletin, February 16, 2023. https://doi.org/10.1177/01461672231151791

Abstract: Individuals tend to hold a dim view of for-profit corporations, believing that profit-seeking comes at the expense of ethicality. In the present research, we show that this belief is not universal; rather, people associate ethicality with an organization’s size. Across nine experiments (N = 4,796), people stereotyped large companies as less ethical than small companies. This size-ethicality stereotype emerged spontaneously (Study 1), implicitly (Study 2), and across industries (Study 3). Moreover, we find this stereotype can be partly explained by perceptions of profit-seeking behavior (Supplementary Studies A and B), and that people construe profit-seeking and its relationship to ethicality differently when considering large and small companies (Study 4). People attribute greater profit-maximizing motives (relative to profit-satisficing motives) to large companies, and these attributions shape their subsequent judgments of ethicality (Study 5; Supplementary Studies C and D).

In Europe: We find evidence of the preference for having a girl, reflected in an increased probability of not having a second child if the first child is female

The sex preference for children in Europe: Children’s sex and the probability and timing of births. Ewa Cukrowska-Torzewska, Magdalena Grabowska. Demographic Research, Feb 16 2023. DOI: 10.4054/DemRes.2023.48.8

Abstract

Background: The preference for having children of a particular sex may be reflected in fertility behavior. For example, parents who want to have a son may be more likely to have another child if their firstborn child is female or if they have two female children. They may also speed up the conception, resulting in a faster progression to the next child.

Objective: We examine whether there is a sex preference for children in Europe, which is reflected in an increased/decreased probability of having another child and a shorter/longer time to the next birth given the sex of existing children. We distinguish between progression to the second and the third child and different cohorts.

Methods: We model the impact of children’s sex on fertility using event history analysis. We apply mixture cure models, which allow us to distinguish between the probability of experiencing the event of interest and its timing.

Results: We find evidence of the preference for having a girl, reflected in an increased probability of not having a second child if the first child is female. We also find that women who have two children of the same sex are more likely to give birth to a third child.

Contribution: We contribute to research on the sex preference for children by (1) providing a comprehensive analysis of a number of European countries using consistent data and methodology, (2) examining the progression to the second and the third child, (3) distinguishing between different cohorts of women, and (4) applying mixture cure models.

Keywords: Europe, family structure, fertility, gender, progression rate, sex, sex composition, son preference

Increased dominance of heat-tolerant symbionts creates resilient coral reefs in near-term ocean warming

Increased dominance of heat-tolerant symbionts creates resilient coral reefs in near-term ocean warming. Ana M. Palacio-Castro et al. Proceedings of the National Academy of Sciences, 120 (8) e2202388120, February 13, 2023. https://doi.org/10.1073/pnas.2202388120

Significance: Global warming is causing the loss of coral reefs worldwide, as a result of heat-induced coral bleaching and mortality. Here, we examined the potential mechanisms that have increased the heat resistance of dominant framework-building coral taxa (Pocillopora spp.) on reefs in the eastern tropical Pacific. We propose that increasing abundance of a thermotolerant symbiotic alga (Durusdinium glynnii) hosted by these corals has facilitated the maintenance of high coral cover after three mass coral bleaching events. This study reveals a mechanism by which some reefs may be more resilient than previously thought and illustrates how future reefs might still maintain high cover for several decades, albeit with low diversity, provided other stressors are minimized.

Abstract: Climate change is radically altering coral reef ecosystems, mainly through increasingly frequent and severe bleaching events. Yet, some reefs have exhibited higher thermal tolerance after bleaching severely the first time. To understand changes in thermal tolerance in the eastern tropical Pacific (ETP), we compiled four decades of temperature, coral cover, coral bleaching, and mortality data, including three mass bleaching events during the 1982 to 1983, 1997 to 1998 and 2015 to 2016 El Niño heatwaves. Higher heat resistance in later bleaching events was detected in the dominant framework-building genus, Pocillopora, while other coral taxa exhibited similar susceptibility across events. Genetic analyses of Pocillopora spp. colonies and their algal symbionts (2014 to 2016) revealed that one of two Pocillopora lineages present in the region (Pocillopora “type 1”) increased its association with thermotolerant algal symbionts (Durusdinium glynnii) during the 2015 to 2016 heat stress event. This lineage experienced lower bleaching and mortality compared with Pocillopora “type 3”, which did not acquire D. glynnii. Under projected thermal stress, ETP reefs may be able to preserve high coral cover through the 2060s or later, mainly composed of Pocillopora colonies that associate with D. glynnii. However, although the low-diversity, high-cover reefs of the ETP could illustrate a potential functional state for some future reefs, this state may only be temporary unless global greenhouse gas emissions and resultant global warming are curtailed.

One's own recorded voice often sounds so embarrassingly creepy because of the lack of bone conduction that is inevitably present when hearing one’s own voice while speaking.

Bone conduction facilitates self-other voice discrimination. Pavo Orepic, Oliver Alan Kannape, Nathan Faivre and Olaf Blanke. Royal Society Open Science, February 15 2023. https://doi.org/10.1098/rsos.221561

Abstract: One's own voice is one of the most important and most frequently heard voices. Although it is the sound we associate most with ourselves, it is perceived as strange when played back in a recording. One of the main reasons is the lack of bone conduction that is inevitably present when hearing one's own voice while speaking. The resulting discrepancy between experimental and natural self-voice stimuli has significantly impeded self-voice research, rendering it one of the least investigated aspects of self-consciousness. Accordingly, factors that contribute to self-voice perception remain largely unknown. In a series of three studies, we rectified this ecological discrepancy by augmenting experimental self-voice stimuli with bone-conducted vibrotactile stimulation that is present during natural self-voice perception. Combining voice morphing with psychophysics, we demonstrate that specifically self-other but not familiar-other voice discrimination improved for stimuli presented using bone as compared with air conduction. Furthermore, our data outline independent contributions of familiarity and acoustic processing to separating the own from another's voice: although vocal differences increased general voice discrimination, self-voices were more confused with familiar than unfamiliar voices, regardless of their acoustic similarity. Collectively, our findings show that concomitant vibrotactile stimulation improves auditory self-identification, thereby portraying self-voice as a fundamentally multi-modal construct.

1. Introduction

We are all familiar with the strange sensation that occurs when we hear our voice in video or voice recordings [1–5]. Considering the fundamental role our voice plays in our everyday communication, this should be quite surprising. We have a lifelong daily exposure to our voice, higher than exposure even to the most familiar voices. Our own voice is the sound most intimately linked to our self. Although there is ample evidence showing that self-related stimuli are perceived differently and activate distinct cortical regions compared with other, non-self-associated stimuli [6–14], the specific mechanisms of self-voice perception have been surprisingly under-investigated, both in behavioural and neuroimaging studies [15–17]. For instance, the extent to which self-voice perception differs from that of other familiar voices remains poorly understood; as does the extent to which acoustic properties that enable discriminating voices of other people [18] are involved in self-other voice discrimination (VD). A better understanding of self-voice perception is of immediate clinical relevance, as deficits in self-other VD have been related to auditory-verbal hallucinations (AVHs) [19–22] (i.e. ‘hearing voices’), one of the most common [23,24] and most distressing [25,26] hallucinations in a major psychiatric disorder, schizophrenia. Investigating different perceptual factors underlying self-other VD, we here hypothesized that one key contribution would stem from bone conduction and, based on our findings, propose a new experimental paradigm that improves the ecological validity for studying self-voice perception.

A crucial contribution for the perception of our own voice, and our own voice only, comes from bone conduction resulting from speech production/articulation. Under natural conditions, one's spoken voice is transmitted not only through the air, but also, unfailingly through the skull [27,28], which alters self-voice perception in two ways. First, due to the different sound propagation, bone conduction transforms the sound of our voice—specifically, it is assumed to instantiate a low-pass filter [29,30]. Because of the low-frequency emphasis, we hear our voice as lower [29] compared with how our voice sounds to others. Second, next to transforming the sound of our voice, bone conduction conveys additional sensory information, as not only auditory, but also vibrotactile [31] and somatosensory [32,33] signals are involved, resulting from the vibrations of the skull and skin deformation. Thus, self-voice, when heard under natural conditions, is not only an auditory but rather a multi-modal percept.

One reason for the scarcity of self-voice studies probably lies in methodological obstacles faced when creating appropriate experimental stimuli. Without bone conduction, prior self-voice studies inevitably contain a perceptual mismatch between the experimental self-voice stimuli (e.g. presented through air-conducting loudspeakers) and the actual self-voice. In fact, the majority of studies that compared recognition of self-voice versus other voices reported lower accuracy rates and higher response times for self-voice compared with other voices [16,34–48]. Early self-voice studies suggested that this discrepancy between self- and other voices might result from a lower previous exposure to self-voice in voice recordings [34,35,37]. However, similar behavioural differences still persist [16,36–41,45], with a higher exposure to recorded self-voice through contemporary technology (e.g. voice messages and video recordings). Moreover, more recent self-voice paradigms often demonstrate ceiling effects [37,39–41,46–49], e.g. high accuracy rates in all experimental conditions, reflecting a need for more sensitive experimental paradigms. To account for the aforementioned ecological discrepancy, several studies investigated if acoustic transformations (e.g. low-pass or other types of filters) of air-conducted self-voice stimuli would render the self-voice more natural to the listeners. These attempts, however, yielded contradictory results [50–54], as they indicated preferences for different acoustic transformations. Crucially, these studies manipulated only one aspect related to bone conduction effects on self-voice (i.e. acoustic transformations) and neglected the additional vibrotactile stimulation. In order to better approximate natural self-voice, experimental self-voice stimuli should be accompanied with the concomitant vibrotactile stimulation resulting from the vibrations of the skull. Here, we address this by providing vibrational input through a bone conduction headset and investigate whether it improves self-voice perception, as opposed to auditory input alone.

In a series of three behavioural studies in independent cohorts, and using a new self-voice perception paradigm, we investigated the following three main perceptual factors of self-other VD: (i) sound conduction type (air versus bone), (ii) other-voice familiarity (familiar versus unfamiliar), and (iii) acoustic voice parameters. Using voice-morphing technology [55] and bone conduction headphones, we designed a psychophysical self-other VD task to investigate the nature of perceptual differences in self-other VD, while trying to avoid ceiling effects. Participants heard short voice morphs of their own and other people's vocalizations (phoneme /a/) and indicated whether the morphs more closely resembled their own or someone else's voice. In Study 1 (N = 16), we investigated differences in self-other VD as a function of sound conduction (air, bone) and how this is modulated by previous exposure to self-voice [34,35,37]; in Study 2 (N = 16), we extended this to familiar-other VD in order to investigate whether the bone conduction effects are specific for self-voice, or generalize to other familiar voices [56,57]. In Study 3, we set out to replicate Studies 1 and 2 within a single, larger cohort (N = 52). We, furthermore, included an additional self-familiar VD task and a control self-voice recognition task (without voice morphing) and investigated the acoustic parameters of all tested voices [18]. We hypothesized that bone conduction would facilitate self-voice perception in self-other VD (bias or increased sensitivity) (Study 1) but would not affect familiar-other VD task (Study 2). We further hypothesized that bone conduction effects would be more prominent without exposure to the self-voice used in our experiment prior to the task—i.e. when the task difficulty is increased (Studies 1 and 2)—and that they would occur regardless of other-voice familiarity [56,57] (Study 3).

If we use multi-state commuting zones, which provide superior definitions of local economic areas, we find a robust negative relationship between minimum wages and employment.

What's Across the Border? Re-Evaluating the Cross-Border Evidence on Minimum Wage Effects. Priyaranjan Jha, David Neumark, Antonio Rodriguez-Lopez. Calif Univ, Irvine, November 2022. https://www.socsci.uci.edu/~jantonio/Papers/minwage_czones.pdf

Abstract: Dube, Lester, and Reich (2010) argue that state-level minimum wage variation correlated with economic shocks generates spurious evidence that higher minimum wages reduce employment. Using minimum wage variation within contiguous county pairs that share a state border, they find no relationship between minimum wages and employment in the U.S. restaurant industry. We show that this result is overturned if we use instead multi-state commuting zones, which provide superior definitions of local economic areas. Using the same within-local area research design—but within cross-border commuting zones—we find a robust negative relationship between minimum wages and employment.

JEL Classification: J23, J38

Check also Exploiting minimum-wage variation within multi-state commuting zones, we document a negative relationship between minimum wages and firm variety; a binding minimum wage further reduces the mass of firms, exacerbating the distortion

Jha, Priyaranjan and Rodriguez-Lopez, Antonio, Minimum Wage and Firm Variety (2021). CESifo Working Paper No. 9312, SSRN: https://ssrn.com/abstract=3932020

Paying Moms to Stay Home, Finland Edition: Home care benefits negatively affect the early childhood cognitive test results of children, decrease the likelihood of choosing academic high school, and increase youth crimes

Paying Moms to Stay Home: Short and Long Run Effects on Parents and Children. Jonathan Gruber, Tuomas Kosonen & Kristiina Huttunen. NBER Working Paper 30931, Feb 2023. DOI 10.3386/w30931

Abstract: We study the impacts of a policy designed to reward mothers who stay at home rather than join the labor force when their children are under age three. We use regional and over time variation to show that the Finnish Home Care Allowance (HCA) decreases maternal employment in both the short and long term. The effects are large enough for the existence of home care benefit system to explain the higher short-term child penalty in Finland than comparable nations. Home care benefits also negatively affect the early childhood cognitive test results of children, decrease the likelihood of choosing academic high school, and increase youth crimes. We confirm that the mechanism of action is changing work/home care arrangements by studying a day care fee reform that had the opposite effect of raising incentives to work – with corresponding opposite effects on mothers and children compared to HCA. Our findings suggest that shifting child care from the home to the market increases labor force participation and improves child outcomes.

We are more interested in the immoral and amoral than in the normies

Wylie, Jordan, and Ana P. Gantman. 2022. “People Are Curious About Immoral and Morally Ambiguous Others.” PsyArXiv. May 30. doi:10.31234/osf.io/zmcta

Abstract: Looking to the popularity of superheroes, true crime stories, and anti-heroic characters like Tony Soprano, we investigated whether people are curious for moral extremity, especially moral badness. Across five experiments (N = 2,284), we examine moral curiosity, testing under what conditions moral minds spark information-seeking. In Experiment 1, we find that among the most widely watched Netflix shows over a five-month period, the more immoral the protagonist, the more hours people spent watching. In Experiments 2a and 2b, we find that when given a choice to learn more about morally good, bad, ambiguous, or average others, people preferred to learn more about morally extreme, both good and bad. Experiment 3 reveals that people are more curious about explanations for morally bad and ambiguous people compared to morally good ones. Finally, Experiment 4 tests the uniqueness of curiosity for moral ambiguity. We find that people are more drawn to moral rather than aesthetic ambiguity, suggesting that ambiguity, which is cognitively taxing and sometimes avoided, piques curiosity in the moral domain. These findings suggest that deviations from moral normativity, especially badness, spur curiosity. People are often curious about the morally corrupt; villains and antiheroes alike prompt engagement rather than avoidance.

This is how we are: "People are more likely to engage in critical thinking when assessing others' reasoning"

Anchoring in a Social Context: How the Possibility of Being Misinformed by Others Impacts One's Judgment. Joana Reis, Mário B. Ferreira, André Mata, Amanda Seruti and Leonel Garcia-Marques. Social Cognition, Vol 41, Issue 1, February 2023. https://doi.org/10.1521/soco.2023.41.1.67

Abstract: Building on research about naïve theories of biases, we propose that people are more likely to engage in critical thinking when assessing others’ reasoning. Hence, anchoring effects should be reduced when anchor values are presented as others’ estimates and people perceive others as less knowledgeable (i.e., more prone to biases) than themselves. Three experiments tested this hypothesis by presenting the same anchors as other participants’ answers or without a specified source. This source manipulation was combined with explicit forewarnings about the anchoring effect, which have been shown to trigger debiasing efforts. In support of our hypothesis, results showed that anchors provided by a social source effectively reduced the anchoring effect and did so in a more reliable way than forewarnings. Furthermore, the response-time analysis in two of the experiments suggests that such attenuation was the result of deliberate adjustment.

Scientists could accurately predict the sex of the subject on the basis of the greater brain activity elicited by porn in men

Pattern recognition reveals sex-dependent neural substrates of sexual perception. Vesa Putkinen, Sanaz Nazari-Farsani, Tomi Karjalainen, Severi Santavirta, Matthew Hudson, Kerttu Seppälä, Lihua Sun, Henry K. Karlsson, Jussi Hirvonen, Lauri Nummenmaa. Human Brain Mapping, February 11 2023. https://doi.org/10.1002/hbm.26229

Abstract: Sex differences in brain activity evoked by sexual stimuli remain elusive despite robust evidence for stronger enjoyment of and interest toward sexual stimuli in men than in women. To test whether visual sexual stimuli evoke different brain activity patterns in men and women, we measured hemodynamic brain activity induced by visual sexual stimuli in two experiments with 91 subjects (46 males). In one experiment, the subjects viewed sexual and nonsexual film clips, and dynamic annotations for nudity in the clips were used to predict hemodynamic activity. In the second experiment, the subjects viewed sexual and nonsexual pictures in an event-related design. Men showed stronger activation than women in the visual and prefrontal cortices and dorsal attention network in both experiments. Furthermore, using multivariate pattern classification we could accurately predict the sex of the subject on the basis of the brain activity elicited by the sexual stimuli. The classification generalized across the experiments indicating that the sex differences were task-independent. Eye tracking data obtained from an independent sample of subjects (N = 110) showed that men looked longer than women at the chest area of the nude female actors in the film clips. These results indicate that visual sexual stimuli evoke discernible brain activity patterns in men and women which may reflect stronger attentional engagement with sexual stimuli in men.

5 DISCUSSION

Our main finding was that sexual stimuli elicit discernible patterns of brain activation in men and women. The GLM analysis revealed that sexual movie clips and pictures elicited widespread activation across the brain in both sexes: Activations were observed in regions associated with reward and emotion (e.g., brainstem, basal ganglia, thalamus, ACC, amygdala, and medial prefrontal cortex) and in somatosensory and motor cortices (pre- and postcentral gyrus, SMA) implicated in sexual arousal (Georgiadis & Kringelbach, 2012). Activations were also observed in visual regions in the occipital and inferior temporal cortices and in the dorsal attention network (frontal eye fields, FEF and intraparietal sulcus, IPS). Men showed stronger responses than women particularly in visual regions in the occipital cortex and fusiform gyri, in the dorsal attention network as well as in various prefrontal regions. Notably, using multivariate pattern classification we were able to accurately predict the sex of the individual subjects. The classifier generalized across the movie and picture experiments, underlining the consistency of the sex-specific response patterns. These results indicate that, although visual sexual stimuli engage similar networks in men and women, brain activity patterns induced by such stimuli are different across sexes.

5.1 Brain activity patterns induced by visual sexual stimuli predict individuals' sex

Using multivariate pattern classification of the brain responses to the sexual movies and pictures, we were able to accurately classify the subjects as men or women. This indicates that sex differences in the brain responses to sexual signals are robust enough to differentiate men and women at the individual subject level. To our knowledge, there are no previous studies employing sex classification with visual sexual stimuli, but the classification accuracies achieved in the current study are comparable with those obtained in sex classification with resting-state fMRI (Satterthwaite et al., 2015; Weis et al., 2020; Zhang et al., 2018; Zhang et al., 2020) and functional connectivity during a semantic decision task (Xu et al., 2020). The accuracy was better in the movie (76%) than in the picture experiment (66%). This likely reflects the fact that audiovisual movies are more representative of the natural sociosexual environment, and consequently activate the brain more strongly and consistently than still photos (Hasson et al., 2010). Importantly, above chance level classification was achieved even with cross-classification where the classifier was trained on the data from one experiment and tested on data from the other indicating that the male/female-typical brain activation patterns evoked by sexual signals were consistent across the experiments. This indicates that the sex-specific brain responses reflected the processing of the sexual content shared across the dynamic videos and still pictures.

Virtually the same regions showing sex differences in the GLM analysis (see below) also contributed the most to the classification with SVM in both experiments as indexed by the high correlation between the SVM weights and the beta values for the sex difference 2nd level contrasts (r = .7 for the movie experiment and r = .6 for picture experiment). Namely, occipital cortex and fusiform gyrus and frontal regions showed strong weights indicative of male category while temporal regions showed the strong voxel weights indicative of female category (see Figure S4). Interestingly, above chance level sex classification was obtained even with the responses to the control dimension. However, the cross-classification between the responses to the control dimension and the sexual stimuli was at chance level indicating that different activity patterns contributed to the sex classification for sexual versus nonsexual stimuli. In line with this, the spatial distribution of the SVM weight across the brain for the sexual stimuli and the control dimension were dissimilar as illustrated by the low correlation between the voxel weight maps for the sexual stimuli and the control dimension (r = −.17 for the movie experiment and r = .07 for the pictures experiment).

Although the brain activity patterns evoked by visual sexual stimuli were predictive of subject sex, some subjects were misclassified demonstrating that these brain activity patterns were not fully sexually dimorphic (compare Joel & Fausto-Sterling, 2016). Classification accuracy is partly determined by methodological factors such as the training set sample size (Balki et al., 2019) but some previous studies suggest that sex misclassification may also reflect a characteristic cognitive or affective profile (Satterthwaite et al., 2015; Zhang et al., 2021). In the current study, the misclassified men reported lower negative emotions toward pornography than the correctly classified men, but no other differences were found between the correctly and incorrectly classified subjects (see Data S1). Interestingly, those subjects who identified themselves as bisexual were no more likely to be misclassified than those who identified themselves heterosexual suggesting that brain activity patterns evoked by sexual stimuli are not dependent on bisexual vs. heterosexual orientation. It is possible that factors such as sexual history or more nuanced sexual preferences may contribute to the misclassification.

5.2 Sex-dependent activation of visual and attentional circuits

Sexual stimuli activated occipitotemporal visual regions consistently in both experiments, suggesting attentional modulation of visual cortical activity for sexually salient stimuli. Event-related potential studies indicate that human bodies with visible (vs. hidden) sexual signals induce amplified temporocortical responses already <200 ms from stimulus onset demonstrating facilitated processing of visual sexual cues early in visual processing stream (Alho et al., 2015; Hietanen et al., 2014; Hietanen & Nummenmaa, 2011). Occipital activity was particularly strong in the putative body sensitive regions (the “extrastriate body area”) in the lateral occipital cortex (Downing et al., 2001) suggesting amplified processing of sexual information in the human body recognition systems (e.g., Ponseti et al., 2006). Men showed stronger activity than women in a cluster extended from V2 along the fusiform gyrus (compare Sabatinelli et al., 2004; Sylva et al., 2013; Wehrum et al., 2013) which suggests that sexual stimuli trigger stronger attentional amplification of visual cortical activity in men than in women. Heightened attention toward visual sexual cues facilitates sexual arousal (Dawson & Chivers, 2016) which may explain previous findings that the activation of occipitotemporal visual regions is positively associated with measures of penile erection and subjective sexual arousal (Arnow et al., 2002; Moulier et al., 2006).

Eye-tracking studies indicate that men show an attentional bias toward the explicitly sexual aspects of visual sexual stimuli (Nummenmaa et al., 2012; Rupp & Wallen, 2007). Our control experiment with eye tracking revealed that men looked longer at the chest area of the nude female actors in the movie clips than women did (approximately 7% vs. 5% of the video duration in men vs. women, respectively). Women, in turn, tended to look at the male actors faces slightly longer than men did. These subtle sex differences in the locus of attention may partly account for the sex differences in brain activation in the visual cortices (compare Dolcos et al., 2020; Ferri et al., 2013). Both the sexual videos and pictures activated intraparietal sulcus (IPS) and frontal eye fields (FEF) which are central nodes in the dorsal attention network supporting controlled, top-down attention (Corbetta & Shulman, 2002). In both experiments, men showed stronger activation in a parietal cluster that extended to the IPS as well as in middle frontal gyrus/precentral gyrus extending to the FEF suggesting that visual sexual stimuli engage dorsal attention network more strongly in men that in women. Interestingly, the eye tracking data also revealed that faces were the most attended regions in the sexual scenes. This accords with the well-known attentional bias towards faces and suggests that during sexual contact the partner's face conveys important information regarding enjoyment and sexual arousal thus warranting preferetntial attention over genitals and other erogenous zones.

Women showed stronger activation than men only in the movie experiment in auditory cortical regions. This result suggests that women responded more strongly to the audio track in the sexual video clips which consisted mostly of nonverbal female vocalizations communicating sexual pleasure. A number of studies have shown that affective vocalizations, including sexual ones (Fecteau et al., 2007), elicit stronger auditory cortical activity than neutral voices (Frühholz et al., 2016). Behavioral studies suggest a slight female advantage in emotion recognition from nonverbal emotional vocalizations (Thompson & Voyer, 2014) but sex differences in affective sound processing have not been studied extensively with neuroimaging (however, see Ethofer et al., 2007). Our results tentatively suggest that women respond stronger to nonverbal sexual vocalizations and thereby that the stronger male reactivity to sexual cues might be specific to visual domain. However, as attention toward visual stimuli attenuates auditory cortical activity (Johnson & Zatorre, 2006; Molloy et al., 2015), another explanation is that this group difference reflects stronger reduction in auditory cortical activity in men due to stronger attention toward the visual sexual cues in the videos in men compared to women. In line with this interpretation both men and women showed reduced auditory cortex activity for the sexual videos as indicated by the negative beta weights in auditory cortex (Figure 5).

Evolutionary accounts posit that men and women have evolved different mating strategies in domains where they have faced different adaptive challenges (Buss & Schmitt, 1993). Lower obligatory parental investment in men has presumably given rise to the stronger preference for short-term mating and sexual variation in men, as these have increased the probability of genetic success more for men than for women. Men may also have evolved a preference for physical features associated with youth since such cues signal fertility and many years of potential future reproduction (Buss & Schmitt, 2019). The type of pornography consumed by men often simulates short-term sexual encounters with novel young women (Malamuth, 1996; Salmon & Diamond, 2012). Thus, men's higher attentional engagement with sexual stimuli might reflect evolved preferences for sexual variety and physical cues of reproductive potential. Such biological biases probably interact with cultural norms in shaping sex-typical preferences as evidenced by cross-cultural variation and changes across time in the magnitude of these sex differences (Buss & Schmitt, 2019; Petersen & Hyde, 2011).

5.3 Emotion circuit activation in men and women

Both men and women experienced strong positive emotions and only weak negative emotions toward pornography although men reported slightly higher feelings of sexual arousal and joy and less shame than women. In accordance with the incentive value of sexual stimuli, both experiments activated limbic and mesolimbic regions associated with reward and emotion such as the ventral striatum and amygdala in both men and women. Unlike some previous studies, we did not observe sex differences in the activation of the amygdala (Hamann et al., 2004) or NAc (Wehrum-Osinsky et al., 2014) suggesting that activity evoked by visual sexual stimuli in these regions does not reliably differentiate men and women. The sexual stimuli also activated the primary and secondary somatosensory cortices and insula in both men and women in accordance with previous studies (Arnow et al., 2009; Ferretti et al., 2005). These regions contribute to emotion via the processing of bodily sensations and interoceptive feedback (Craig, 2002) and SII is more generally involved in the perception of touch (Keysers et al., 2010). We also observed activation in the ACC, which is a common finding in studies employing visual sexual stimuli (Stoléru et al., 2012) presumably because cingulate activity is coupled with autonomic arousal (Beissner et al., 2013). Overall, the sex differences observed in the GLM analysis were most consistent in cortical regions although activity in the brainstem and thalamus were also stronger in men than in women in the pictures experiment.

5.4 Sex differences in neural substrates of sexual perception: State of the evidence

The recent meta-analysis of Mitricheva et al. (2019) found no evidence of sex differences in brain responses to visual sexual stimuli. However, Poeppl et al. (2020) re-analyzed these data with a number of methodological improvements, such as the exclusion of ROI analyses, and found more consistent activation in ACC and hypothalamus in men and in lateral occipital cortex in women. We also found a sex difference in a frontal cluster partly overlapping with the ACC but did not replicate the hypothalamic and occipital effects.

One possible source of the discrepancies between our results and these meta-analyses is that the latter were not based on direct comparisons between sexes in the original studies. Instead, both meta-analyses compared separate Activation Likelihood Estimation (ALE) maps for men and women that were computed mostly from studies with only men or women as subjects. This approach can reveal sex differences in how consistently a given region is activated in different studies (i.e., sex difference in convergence), but cannot uncover the consistency of sex differences in brain activation across studies (i.e., convergence of sex differences) (Müller et al., 2018). Such meta-analyses may also be confounded by methodological differences between studies with only men or women as participants. A meta-analysis of direct comparisons between men and women is precluded by the scarcity of pertinent high-quality studies: Mitricheva et al included only 11 studies with both men and women, and most of these were underpowered for reliable group comparison (Hamann et al., 2004; Klucken et al., 2009) or did not perform a whole brain analysis of the sex differences (Strahler et al., 2018). Notably, the only study with a whole brain GLM analysis of sex differences and a sample size comparable to ours (Wehrum et al., 2013) revealed stronger responses to sexual pictures in men than women in the thalamus and occipital and parietal cortex in line with our results. Thus, we provide much-needed data on sex dependency of neural responses to sexual stimuli and pave way for robust meta-analyses of such sex differences.

5.5 Limitations

Subject-specific emotion ratings and physiological arousal responses were not acquired from the participants in the fMRI experiment; thus we could not directly link the hemodynamic data with direct indices of sexual arousal. The current study specifically focused sex differences in brain responses to stimuli representative of “mainstream” pornography typically consumed more by men than women and we did not attempt to balance how sexually arousing or interesting the stimuli were for the male and female participants (cf. Janssen et al., 2003; Laan et al., 1994). The majority of our subjects identified as exclusively heterosexual and thereby we were unable to test the effects of sexual preference irrespective of gender and our results may not generalize to individuals with non-heterosexual preference.

Do humans agree on which body odors are attractive, similar to the agreement observed when rating faces and voices?

Do humans agree on which body odors are attractive, similar to the agreement observed when rating faces and voices? Megan Nicole Williams, Coren Lee Apicella. Evolution and Human Behavior, February 14 202. https://doi.org/10.1016/j.evolhumbehav.2023.02.002

Abstract: Studies of mate choice from an evolutionary perspective often begin by investigating whether individuals of one sex share similar preferences for mates. Evidence for shared preferences is often interpreted as support for the hypothesis that preferences are adaptations that have evolved to select high-quality mates. To date, the importance of body odor in human mate choice is uncertain because fundamental questions, such as whether preferences for body odor are shared, have not yet been systematically explored. Here, we asked groups of heterosexual men and women from the University of Pennsylvania to rate the attractiveness of body odors, faces, and voices of opposite-sex individuals. We used our data to produce quantitative estimates of the amount of rater agreement for each of the three modalities of attractiveness, applying a uniform methodology that facilitates cross-modality comparisons. Overall, we found evidence of agreement within all three modalities. Yet, our data also suggest a larger component of attractiveness judgments that can be attributed to personal preferences and idiosyncratic noise. Importantly, our results provide no evidence that agreement regarding odor attractiveness is substantially quantitatively different from the amount of agreement found in other modalities that have been the focus of most previous work. To the extent that evidence exists of shared preferences for faces and voices, our results reveal evidence of shared preferences for body odors.

Keywords: OlfactionBody odorMate choiceFace attractivenessVoice attractivenessMultimodal perception

4. Discussion

Possibly the most conclusive and replicable finding in social psychology is that attractiveness is an important factor in social interactions (for review see, Grammer et al., 2003). Symons (1979) suggested shared attractiveness preferences are evolved adaptations for choosing fitness-enhancing mates, and since the 1990s, evidence has accumulated demonstrating shared attractiveness preferences for others' faces (e.g., Grammer & Thornhill., 1994; Langlois & Roggman, 1990; Mealey et al., 1999; Perrett et al., 1999; Rhodes, Proffitt, Grady and Sumich, 1998, Rhodes, Sumich and Byatt, 1999; Rhodes & Tremewan, 1996), bodies (e.g., Singh, 1993; Singh et al., 2010; Singh & Young, 1995), and voices (Collins, 2000; Feinberg et al., 2005; Puts et al., 2013). Here, we investigated whether there is evidence of shared attractiveness preferences for body odor, as has been observed in these other modalities.

To provide a benchmark from which we could assess our evidence for agreement in judgments of body odors, we used the same methodology, sample, and analysis to also examine agreement in judgments of faces and voices. Thus, any differences in variance attributable to agreement between modalities could not be caused by differences in the sample or analysis. We found no significant differences in levels of agreement in attractiveness ratings between modalities. However, there was evidence of little agreement overall in female ratings of men's attractiveness when using the individual-agreement ICC. Yet, we do report fair to good agreement in all attractiveness modalities using the average-agreement ICC (k = 4). The average-agreement ICC removes measurement noise caused by any one rater's ratings; thus, we expected that the average-agreement estimates would be higher than the individual-agreement estimates. For male ratings of women's attractiveness, we found that agreement in the attractiveness modalities was statistically distinguishable from zero, but low. Our samples of male and female raters were not large enough to detect sex differences in agreement in attractiveness preferences. We estimated the magnitude of the difference between male and female rater agreement for each modality, but the standard error of each estimated sex difference was too large to allow for conclusions from this observation. Few studies have evaluated sex differences in rater agreement for judgments of attractiveness, however there is some research to suggest there are no significant differences in agreement (e.g., Coetzee et al., 2014) or greater consensus among men (e.g., Rhodes et al., 1998). Higher agreement in men is consistent with the idea that attractiveness plays a larger role in male mate choice whereas, for example, social status is more important for female mate choice (Buss, 1989). However further research is necessary using samples large enough to detect small sex differences and evaluating the underlying fitness markers influencing attractiveness judgments in each sensory modality. Again, encouragingly our findings indicate statistically equivalent levels of agreement in judgments of attractiveness for each modality of attractiveness (i.e., face, voice, and odor) within both sexes. So, although we cannot make a strong claim for evidence of evolved attractiveness preferences, especially because we are unsure of how much agreement would constitute evidence, our data do demonstrate that to the degree that shared preferences exist for faces and voices, they also exist for body odors.

While our estimated agreement for within-sex judgments of opposite-sex attractiveness in each modality seems lower than estimates reported in earlier studies, the parameters we used were different and not necessarily at odds. For example, Thornhill and Gangestad (1999) measured consistencies for male (n = 61) and female (n = 48) ratings of opposite-sex body odors using Cronbach's alpha (α = 0.66, high-fertility female raters; α = 0.90, low-fertility female raters; α = 0.90, male raters). Similarly, Lobmaier, Fischbacher, Wirthmüller, and Knoch (2018) reported an ICC of 0.983 for male (n = 55) ratings of women's (n = 28) body odors. As discussed at length elsewhere (Hehman, Sutherland, Flake & Slepian, 2017; Hönekopp, 2006), high alphas and average-agreement ICC estimates do not necessarily provide evidence of strong interrater agreement. The fundamental difficulty is that these parameters are strongly influenced by the number of items (here, raters), which often varies across studies, hampering comparability. Likewise, an ICC near one is very hard to interpret unless which of the many possible ICCs have been estimated is made explicit (McGraw & Wong, 1996). Through personal correspondence (June 8, 2020), we were able to determine that the parameter estimated by Lobmaier, Fischbacher, Wirthmüller, and Knoch (2018) was the average-agreement ICC for n = 55 male raters. Because their study estimated a different parameter than the present study, the lower estimates we have reported are not at odds with what they found. On the contrary, the value of ρA, 1 implied by Lobmaier, Fischbacher, Wirthmüller, and Knoch (2018) estimate of ρA, 55 is around 0.5 and hence, in the same ballpark as the estimates of individual agreement reported in the present study, see Bliese (2000) for the formulae needed to rescale parameter estimates for comparability.

Misinterpretations of Cronbach's alpha and the average-agreement ICC can cause overestimations of the strength of evidence for shared attractiveness preferences because the contribution of personal preference is typically unreported or defined as random noise (Hönekopp, 2006). Our analysis not only reported the average-agreement ICC (k = 4), but also the individual-agreement ICC, which reports the correlation between the individual judgments of two raters assigned to the same donor. The individual-agreement ICC parameters reported here show that there is some agreement between raters' judgments in each attractiveness modality that can be attributed to a shared preference, but a larger component also exists that can be attributed to personal preference and noise. Our individual-agreement ICC estimates are in line with recent research using statistical methods accounting for variances in attractiveness judgments of faces attributed to both donor (i.e., shared preference) and rater (i.e., personal preference) characteristics (e.g., Hehman, Sutherland, Flake, & Slepian, 2017; Hönekopp, 2006). For example, Hönekopp's (2006) pioneering study found that in contrast to the prevailing view that facial attractiveness judgments are largely based on donor characteristics and shared universally, variation in judgments of attractiveness were equally explained by perceiver characteristics (i.e., personal preference). In experiment 2, which used a heterogenous racial sample similar to our sample of participants, Hönekopp (2006) estimated that 56% of variance in attractiveness judgments is attributable to the rater (i.e., personal preference). Thus, future work should explore the relative contributions of personal and shared preferences for body odors attractiveness judgments and investigate the underlying fitness markers influencing each.

4.1. Study limitations

Though our findings support the hypothesis that shared preferences for body odors exist to the extent that shared preferences for faces and voices exist, convenience sampling limits the strength of our interpretation. The current study cannot fully distinguish between attractiveness preferences that persist today because past selection favored reliable developmental patterns and preferences that exist because selection favored labile and culturally responsive preferences, since we investigated preferences in a single society. In general, cross-cultural research on odor perception is scant, particularly for mate choice. However, evidence shows that in traditional societies where odor is more significant to daily activities, such as food foraging, olfactory performance and cognition are superior to those of individuals living in industrialized cities (Burenhult & Majid, 2011; Majid & Burenhult, 2014; Majid & Kruspe, 2018; Sorokowska, Sorokowski, Hummel, & Huanca, 2013; Wnuk & Majid, 2012). Future research should investigate body odor preferences cross-culturally. Facial averageness and symmetry are generally accepted as cues of mate quality, in part because both predict attractiveness judgments across different societies (e.g., Apicella, Little, & Marlowe, 2007; Cunningham, Roberts, Barbee, Druen, & Wu, 1995; Jones & Hill, 1993; Little, Apicella, & Marlowe, 2007; Rhodes et al., 2001). Although demonstrating that, to a degree, some men and women generally smell more attractive than others is a promising first step, additional steps must be taken before we can conclude body odor preferences are adaptations for optimal mate selection.

In addition, we used a racially heterogenous sample to estimate agreement in judgments of attractiveness. Therefore, our estimates of agreement are possibly deflated in comparison to if we had used a racially homogenous sample. Race has been demonstrated to influence attractiveness preferences for faces and voices (e.g., Wheatley et al., 2014). Unfortunately, it was not feasible with our sample to perform a robustness analysis estimating interrater reliability within independent homogenous subgroups of participants.

Further, outside of a controlled laboratory setting, humans often wear fragrances, shower, and choose to eat food regardless of their aromatic properties. While controlling for these variables by instituting a two-day washout period before odor sampling is standard procedure in this literature, we are unaware of studies demonstrating that two days are adequate to return a donor's “natural” body odor. Thus, these methods could result in evidence that raters agree on odors but not necessarily “natural” body odors.

Finally, we did not control for potential menstrual cycle effects and oral contraception usage. We initially planned to analyze hormone data, which would have been used to assess women's oestradiol and progesterone levels. This hormone data would have been indicative of cycle phase. However, we were not able to assay our samples due to laboratory and labor disruptions associated with the COVID-19 pandemic. Although menstrual cycle effects are heavily debated (Gildersleeve, Haselton, & Fales, 2014; Harris, 2011, Harris, 2013; Harris, Chabot, & Mickes, 2013; Harris, Pashler, & Mickes, 2014; Wood & Carden, 2014; Wood, Kressel, Joshi, & Louie, 2014), some studies demonstrate that menstrual cycle phase and hormonal contraceptive use affect women's perceptions of men's body odor (Grammer, 1993; Havliček, Roberts, & Flegr, 2005; Hummel, Gollisch, Wildt, & Kobal, 1991; Sorokowska, Sorokowski, & Szmajke, 2012; Thornhill, Chapman, & Gangestad, 2013), faces (e.g., Ditzen, Palm-Fischbacher, Gossweiler, Stucky, & Ehlert, 2017; Johnston, Hagel, Franklin, Fink, & Grammer, 2001; Little, Burriss, Petrie, Jones, & Roberts, 2013; Little & Jones, 2012; Penton-Voak et al., 1999; Penton-Voak & Perrett, 2000), and voices (Feinberg et al., 2006; Pisanski et al., 2014; Puts, 2005, Puts, 2006). Conversely, other studies cast doubt on the existence of cycle shifts in preferences for faces (e.g., Jones et al., 2018; Marcinkowska, Hahn, Little, DeBruine, & Jones, 2019) and voices (e.g., Jünger et al., 2018). Yet, because we did not collect the necessary data to examine menstrual cycle effects in the current study, we cannot contribute to this important debate in a meaningful way.